Adhesive and paint compositions have been applied to polar substrates, such as glass, cellulose and ceramic materials. However, the bond between the composition and the polar substrate is often subject to failure under conditions of stress, high humidity, and elevated temperatures. Adhesion promoters are often incorporated into such compositions or coated on the substrate to improve the adhesion of the composition to the substrate. Typical of such adhesion promoters for polymeric compositions are silanes.
As is known in the art, incorporating a polar functional group, such as pentavalent phosphorus, into a polymer increases the adhesion of the polymer to polar substrates. Amines and other species having lone pairs of electrons are also known to coordinate strongly to polar surfaces. Additionally, amines are known as epoxy curing agents. We have now synthesized a class of epoxy curing agents containing both amino and pentavalent phosphorus moieties and found them useful as adhesion promoters for epoxy resins. Thus, these organophosphorus enamines may be employed to cure epoxy resins while providing improved adhesion of the resin to the substrate. On the other hand, materials such as silanes, while promoting adhesion of an epoxy composition to the substrate, may not be used as the sole curing agent for epoxy materials since they react only to a limited extent with the epoxy resin.